Power systems for powering motors may comprise a plurality of components, such as one or more power generation units, drives line-ups, energy storage modules and a main bus to which the aforementioned components are connectable. For reasons of safety, such systems may be designed with redundancy. This is important in e.g., marine applications, where for example in some applications it is essential that dynamic positioning of a vessel to maintain its position by using its propellers and thrusters can be guaranteed at all times.
At some point a fault, such as a short circuit will inevitably occur in the power system, either in the busbar system, in one of the components of the system, or in a load. In case of a fault, it is important to isolate the fault from the healthy part of the system such that normal power provision can be continued by means of the healthy part, and for protecting the healthy parts from being damaged. For this purpose, a protection system is typically included in the power system. A protection system arranged to handle faults in a power system typically comprise monitoring equipment arranged to monitor electrical parameters such as currents in the power system, and circuit breakers controlled by the monitoring equipment. The circuit breakers are arranged in such a way in the power system that selective fault isolation can be obtained in case of a fault. Existing protection systems can however in some applications be both very expensive and space consuming.
WO2013127575 discloses a DC-power system comprising a main DC bus, a power generating unit arranged to feed the main DC bus, an isolator switch arranged between the main DC bus and the power generating unit for isolating the power generating unit from the main DC bus in case of a main DC bus fault, a drive unit arranged to be fed by the main DC bus, wherein the drive unit comprises a drive unit bus system, converter units connected to the drive unit bus system, and fuses arranged between the drive unit bus system and the converter units for protecting the converter units in case of a drive unit fault. Thereby, the various units in the DC-power system can selectively be protected in case of faults in any of the units or on the main DC bus, without the use of large, space consuming and expensive circuit breakers.